Me and my friend are planning to go over to Wilderness Center at Yosemite Village for wilderness permit for Little Yosemite to go to Half Dome. However, we need to stay somewhere in Yosemite Valley on the night before. Does anyone know a good place to just bum out for the night without having to stay at one of the hotel? It is not possible to get campsite reservation now.

I suppose you could walk around the valley all night. Sleeping in cars, camping outside designated areas, crashing in random chairs around the village, etc. would probably get you thrown out of the park.

You can't sleep in cars inside the park. It'll have to be outside the park in national forest, in areas not posted "no trespassing" or "no parking." That's not going to be easy either, but there are spots along the road to Hetch Hetchy where you can sleep in pullouts.

Sleeping in a car in the park is gambling - I've started night hikes at midnight and rangers come through the lots with flashlights.

Once you have your permit, head over to the backpacker camp. It's attached to the North Pines Camping area by a foot bridge. $5 gets you one night and it's just for wilderness permit holders. I have stayed there many times. It is within walking distance to the Happy Isles trail head too.